Vehicles such as lawn and garden tractors may have PTO driven accessories, such as a lawn mower deck, that may be shut off when the vehicle is operated in reverse. For example, when a vehicle is shifted into reverse with the PTO running, an interlock circuit with a reverse gear switch may disconnect the PTO drive and/or stop the engine. The interlock circuit may prevent all operation of PTO driven accessories while the vehicle is operated in reverse.
In recent years, interlock circuits have been proposed to include sensors that permit limited operation of the PTO when the vehicle is operated in reverse, but stop PTO operation if the sensor detects an object behind the vehicle. Various types of sensors have been proposed for detecting obstacles behind the vehicle, including but not limited to ultrasonic, infrared, or photoelectric sensors.
Some interlock circuits may include two or more sensors, such as those described in U.S. Pat. Nos. 6,021,373; 6,044,632; 6,130,607; and 6,173,233. There is a need for a simple, low-cost interlock circuit for use with a single sensor to detect objects behind a vehicle.
Additionally, interlock circuits proposed for sensors that detect obstacles behind riding lawn mowers and similar vehicles may not provide any assurance that the sensor is operational. There is a need for an interlock circuit that will provide assurance that the sensor is working and/or working correctly.
Additionally, an interlock circuit for a sensor that detects obstacles behind a vehicle is needed that will allow the operator to override and continue using the implement in reverse even if an object is detected behind the vehicle.
Additionally, an interlock circuit for a sensor that detects obstacles behind a vehicle is needed that may be reset and provide a non-intrusion signal after an object clears the field of view.